Shaping die



Dec. 27, 1949 E, BURGER r 2,492,131

SHAPIN'G DIE Original Filed Feb. 23, 1944 2 Sheets-Sheet 1 INVENTORS.LEW/s E. fil/EGEE, :Zs-AW/A/Gs 5- SKIN/Vile,

Arron/95v Dec, 27, 1949 LE. BURGER ETAL SHAPING DIE 2 Sheets-Sheet 2Original Filed Feb. 23, 1944 INVE Patented Dec. 27, 1949 STATES ATENTOFFICE SHAPING DIE fornia Original application February 23, 1944, SerialNo. 523,516. Divided and this application March 31, 1945, Serial No.585,842

3 Claims.

This invention relates to the die stamping art in which metal sheets arestretched and bent into desired shapes by pressing or striking thembetween dies, and more particularly to that phase of the art in which aplurality of sets of dies of successively greater depth are required toproduce the desired shape.

This application is a division of our copending application Serial No.523,516, filed February 23, 1944, and entitled Method of makingpreliminary shaping die, which issued as Patent No. 2,383,706 on August28, 1945.

An object is to provide preliminary dies of superior shape in that theyso prepare the sheet metal for the final dies that the latter canproduce deep and abrupt slopes wihout breaking or excessively thinningor wrinkling the metal.

Heretoiore, when a stamping or drawing operation of more than one stagewas necessary in order to produce a satisfactory deep or abrupt slope ina work sheet, it was the practice to have the dies used in thepreliminary stages made manually by highly skilled pattern makers whoproduced them largely by the process of trial and error and with theexpenditure of a great deal of time.

In accordance with the present invention, We provide a routine procedurefor preparing preliminary dies from finish dies, greatly reducing theamount of time and skill required and yielding dies more uniformlysatisfactory than those formerly made by highly skilled pattern makers.

The present invention is based on the principle that the preliminarydrawing or stamping operations should so shape the sheet that the finaloperation is largely a bending operation, involving relatively littlestretching or compression of the sheet. Hence, we make the preliminarydies with substantially the same absolute area as the final die buthaving less depth so that the projected area is greater. This result isobtained by using as a pattern for making the preliminary die asubstantially non-stretchable, flexible sheet that has been first shapedin the finish die and then flattened out by bending to reduce its depth,A suitable material for such a sheet is wax reinforced by fabric in sucha way as to prevent it from stretching or shrinking, while ermitting itto bend.

A full understanding of the invention may be had from the followingdetailed description with reference to the drawing of a specificprocedure in accordance with the invention.

In the drawing:

Fig. 1 is a perspective View of a pattern for a finish die;

Fig. 2 is a cross section of the pattern of Fig. 1 taken in the plane11-11 and showing a wax pattern sheet formed therein;

Fig. 3 is a perspective view of a pattern for a preliminary stage diemade in accordance with the present invention from the finish pattern ofFig. 1;

Fig. 4 is a cross section of the wax pattern sheet as it appears whenremoved from the pattern of Fig. 2;

Fig. 5 is a cross section of the pattern sheet after it has beenpartially flattened out, the section being taken in the positioncorresponding to the line V-V of Fig. 3;

Fig. 6 is a cross section showing the pattern sheet of Fig. 5 supportedand reinforced with plaster;

Fig. '7 is a cross section showing the reinforced pattern sheet of Fig.6 inverted and mounted in a box ready for casting the plaster pattern ofFig. 3; and

Fig. 8 is an enlarged detail cross section of a portion of the patternsheet.

Referring first to Figs. 1 and 2, there is shown a plaster pattern l0for making a female finish die for use in a drop hammer or the like forshaping sheet metal. In accordance with well known procedure, the diemay be cast in a sand mold, which mold was first formed from the patternll]. Insofar as the present invention is concerned, either the patternIi! or the finish die formed therefrom can be employed since both are ofidentical shape. It is usually most convenient to employ the plasterpattern Hi.

It is to be understood that in the stamping press or drop hammer, a maledie or punch is employed and that the sheet metal to be shaped ispressed or struck between the male and female dies. However, it iscustomary to make the male die or punch from the female die, and hence,it is suificient in connection with the present invention to disclosethe method of preparing the pattern for only the female die, the latterbeing hereinafter referred to as the die.

There is shown in 3, a plaster pattern H for forming the preliminary diewhich is used to shape the sheet metal before it is placed in the finishdie corresponding to the pattern ill of Fig. 1. It will be observed thatthe pattern H of Fig. 3 bears little resemblance to the pattern ll) ofFig. 1, yet the shape of pattern I! is inherently such as to prepare thesheet metal for stamping in the finish die so that it can take the formof the finish die without breaking and without thinning or wrinklingexcessively. The reason for this is that the total surface of thepattern i I is substantially the same as that of Fig. 1, the depth ofpattern ll being substantially less and the projected areacorrespondingly greater. Pattern II is obtained in accordance with thepresent invention by the following procedure:

First there is formed in the finish pattern H] a thin pattern sheet 52of wax reinforced with cheesecloth. This is done by first painting thesurface of the plaster pattern 9 with a thin paint of modeling clay,liquid soap and water to prevent the pattern sheet 52 from sticking tothe plaster. Before this paint has dried, a first sheet 53 (Fig. 8)

of cheesecloth is placed on the pattern ill and pressed into intimatecontact with the surface thereof, the cheesecloth being sufiicientlyyieldable to permit such shaping.

Next, the cheesecloth i3 is coated ith a suitable wax It by applying iton top the cheeseq cloth H3 in melted condition with a brush. At thesame time the cheesecloth is again forced into all the corners of thepattern with the brush. The wax congeals as soon as it applied to thecheesecloth by virtue of conduction of heat therefrom into the plasterpattern, and by repeated applications of the molten wax wi brush, thelayer it of wax is built up to a depth of approximately of an inch.

Next, a second sheet of cheesecloth i5 is pressed into the wax it whilethe latter is relatively soft, this second sheet l5 being laid on thebias with respect to sheet it; that with its threads runhim; atapproximately 45 with respect to the threads of cloth l3. Thereafter, athin coat 16 of wax is brushed on to the cloth l5, thereby completingthe pattern sheet l2 as shown in Fig. 2.

After it has cooled a little more and becomes fairly stiff, the patternsheet if? is removed from the pattern if! by gradually pulling it awaytherefrom with the hands. It comes away quite readily because of thethin coat of modeling clay, liquid soap and water that was placed on theplaster pattern before the pattern sheet was formed. As removed from thepattern iii, the pattern sheet l2 appears as shown in Fig. 4, having theshape of the finish pattern ill. It is then flattened out into the shapeshown in Fig. 5, this flattening operation being performed by pulling hepattern sheet apart with force applied at juxtaposed points on the edgethereof accompanied by slight force applied to the under side of theintermediate portion with the hands. This operation changes the shape ofthe pattern sheet without appreciably changing its area because the twosheets of cheesecloth laid on the bias with respect to each otherlargely prevent stretching of the pattern. Such stretching could not beavoided if the pattern sheet were made of wax alone without any fabricreinforcement.

After the pattern sheet has been flattened as shown in Fig. 5, it isused to cast the preliminary stage plaster pattern shown in Fig. 3 bythe procedure illustrated in Figs. 6 and 7.

Referring to Fig. 6, the pattern i2 is first suping substantially thesame ported at relatively closely spaced points on its under surface bymeans of clay bolsters I! extending upwardly from a supporting table orbase [8, after which a thick layer l9 of plaster of Paris is applied tothe upper surface of the pattern sheet, this layer [9 being formed byapplying plaster in relatively stiff condition with a trowel, or withthe hands.

After the plaster backing H! has set, the assembly of the pattern sheet12 and the backing I 9 is removed from the clay bolsters i1, invertedand supported on clay bolsters 20 extending upwardly from a base 2| asshown in Fig. 7. Thereafter, side walls 22 of wood or other suitablematerial are constructed around the plaster backed pattern sheet to formtherewith a mold into which liquid plaster of Paris can be poured. Whenthis plaster of Paris has solidified and has been removed from the mold,it constitutes the preliminary pattern of Fig. 3.

It willbe observed from the procedure described that the inventionprovides a routine process for developing patterns for preliminary diesfrom patterns of finish dies, requiring very little special skill.Furthermore, the procedure is relatively simpleand does not require muchtime.

In some cases, it is necessary to employ more than one preliminary dieto bring the sheet metal into the final desired form by successivestages, each involving a relatively small change in shape from the nextpreceding stage. Hence, in some instances, it may be desirable to forman intermediate stage pattern from the final pattern and then form afirst stage pattern from the intermediate stage pattern. Under suchconditions, the intermediate stage pattern can be prepared as described,after which a first stage pattern can be prepared from the same waxpattern by further flattening it and increasing its projected area andthenusing it to make themold for casting the first stage pattern.

Although various waxes may be employed .in forming the pattern sheet I2,a composition that has been found suitable in practice consists of amixture of from one-half to two-thirds beeswax with the balance apattern makers wax such as Master sheet wax made by Kindt- Collins Co.of Cleveland, Ohio. If overheated, the wax may become too hard, underwhich condition it may be softened with the addition of a small amountof turpentine.

Various departures from the exact procedure described may be made, whilestill obtaining the advantages of the invention, and the latter istherefore limited only to the extent set forth in the appended claims.

We claim:

1. In the art of sheet stamping and drawing, a preliminary shaping diefor partially forming and preparing sheets for further shaping with asecond die having substantial curvature in all directions, saidpreliminary shaping die having a general configuration similar to thesecond die, and having substantially the same absolute surface areathroughout as the second die, but having less depth and acorrespondingly greater projected area than the second die.

2. In the art of sheet stamping and drawing, a preliminary shaping diefor partially forming and preparing sheets for further shaping with a.second die having substantial curvature in all planes intersecting theworking surface of the die, said preliminary shaping die having the samegeneral configuration as the second die, and havabsolute surface areathroughout as the second die, but having less depth and acorrespondingly greater projected area than the second. (lie, and havingits steepest surfaces substantially less steep than the correspondingsurfaces of the second die.

3. In the art of sheet stamping and drawing,

a series of dies for successively shaping a Work sheet in which all thedies have the same general configuration and are irregularly doublecurved and asymmetrical as to curvature and have the same absolutesurface area, but in which one of the early stage dies has less depthand a corresponriingly greater projected area than the next later stagedie, and in which the steepest surfaces of said early stage die aresubstantially less steep than the corresponding surfaces of said laterstage die.

LEWIS E. BURGER.

JENNINGS B. SKINNER.

REFERENCES SITE?) The following references are of record in the file ofthis patent:

5 UNITED STATES PATENTS Number Name Date 173,954 Hoeltge Feb. 22, 18761,375,305 Maisel Apr. 19, 1921 1,909,930 De Bidder May 23, 19331,932,318 O-estnaes Nov. 27, 1934 2,181,020 Le Jeune Nov. 21, 19392,295,852 Le Jeune Sept. 15, 1942 2,383,706 Burger Aug. 28, 19452,422,325 Wheelon June 17, 1947 FOREIGN PATENTS Number Country Date1,301 Great Britain 1887 225,710 Great Britain 1924 OTHER Die Design andDiernaking Practice, sec. ed. 1941, pub. by The Industrial Press, N. Y.

